Non-volatile memory and the fabrication method thereof

ABSTRACT

A non-volatile memory, which comprises an insulating substrate ( 11 ) that has a first electrode ( 18 ) that extends through the substrate from the front surface to the rear surface thereof; a second electrode ( 13 ) that is formed on one side of the insulating substrate ( 11 ); and a recording layer ( 12 ) that is clamped between the first electrode ( 18 ) and the second electrode ( 13 ) and whose resistance value varies when an electric pulse is applied across the first electrode ( 18 ) and the second electrode ( 13 ); wherein the insulating substrate ( 11 ) has a layered structure composed of an organic dielectric thin film ( 112 ) and an inorganic dielectric layer ( 111 ) that is thinner than the organic dielectric thin film ( 112 ); with the recording layer ( 12 ) being formed on the side on which the inorganic dielectric layer is formed. Use of this non-volatile memory increases the possible number of data writing cycles while saving power.

TECHNICAL FIELD

The present invention relates to a non-volatile memory, and moreparticularly to a non-volatile memory in which data can be recorded(written) or deleted by using the application of current to controlresistance value variations, and to the fabrication method thereof.

BACKGROUND ART

Flash memory, FeRAM, MRAM, phase-change memory, and the like areconventionally known types of non-volatile memory. Recent years havebrought about a demand for high-density memories for use in personaldigital assistants and the like, and therefore non-volatile memoriesthat employ a phase-change technique are attracting widespread attentionand various modifications to them have been proposed (WO, A1 No.98/19350 (Japanese Unexamined Patent Publication No. 2001-502848),etc.).

For example, Japanese Unexamined Patent Publication No. 1997-282723discloses an information-recording device in which the writing ordeleting of data is performed by bringing an electrically conductiveprobe into contact with the surface of a recording medium that containsan amorphous semiconductor thin film.

WO, A1 No. 98/336446 (Japanese Unexamined Patent Publication No.2001-504279) discloses a phase-change non-volatile memory in which, asshown in FIG. 10, a phase-change material layer 83 is formed between alower electrode 81 and an upper electrode 82, whereby the phase-changematerial layer 83 can be charged through the lower electrode 81 and theupper electrode 82. The phase-change material layer 83 comprises achalcogenide material whose phase is reversibly changeable between anamorphous (non-crystalline) state of high resistance and a crystallinestate of low resistance. The material is changed to an amorphous orcrystalline state by the application of current, thereby controlling itsresistance value. For example, when storing (writing) data, thephase-change material layer 83 is changed from the amorphous state tothe crystalline state, lowering the resistance value. When deletingdata, the phase-change material layer 83 is changed from the crystallinestate to the amorphous state, raising the resistance value. Thedifference in resistance value is thus read to allow the phase-changematerial layer 83 to serve as a memory.

In the structure shown in FIG. 10, a joint portion 81 a disposed betweenthe lower electrode 81 and the phase-change material layer 83 isisolated by an insulating layer 84. Here, silicon oxide is preferable asthe material for the insulating layer 84. However, when the jointportion 81 a is insulated using silicon oxide, which is an inorganicdielectric having a relatively high thermal conductivity, a large amountof electric power is needed to write or delete data. This makes itdifficult to save power.

On the other hand, when the insulating layer 84 is made of an organicdielectric, this structure not only writes and deletes data with littlepower consumption but also makes the insulating layer 84 cheaper,lighter in weight, and capable of coping with bending deformation.

However, when using only an organic dielectric as the material for theinsulating layer 84, the number of data rewriting cycles is insufficientbecause the heat withstand temperature of the organic dielectric islower than the melting point of the phase-change material. In otherwords, while deleting data, the joint portion 81 a that is disposedbetween the lower electrode 81 and the phase-change material layer 83momentarily generates heat, which varies the temperature of thephase-change material layer 83 above its melting point (for example,600° C. or higher). On the contrary, when polyimide, which exhibitsexcellent heat resistance properties compared to other organicdielectrics, is used as the material for the insulating layer 84, theinsulating layer 84 can only withstand temperatures of approximately500° C., even if the heating is momentary. As a result, the insulatinglayer 84 near the joint portion 81 a decomposes while repeatedlyrewriting data. This deteriorates the electrical properties andmechanical stability of the lower electrode 81 and the phase-changematerial layer 83.

DISCLOSURE OF THE INVENTION

The present invention aims to solve these problems and to provide anon-volatile memory that can increase the possible number of datarewriting cycles while lowering power consumption, and the fabricationmethod thereof.

The objects of the present invention are achieved by a non-volatilememory comprising an insulating substrate having a first electrodeextending through the substrate from the front surface to the rearsurface thereof; a second electrode formed on one side of the insulatingsubstrate; and a recording layer that is clamped between the firstelectrode and the second electrode and whose resistance value varieswhen an electric pulse is applied across the first electrode and thesecond electrode; the insulating substrate having a layered structurecomposed of an organic dielectric thin film and an inorganic dielectriclayer that is thinner than the organic dielectric thin film, with therecording layer being formed on the side on which the inorganicdielectric layer is formed.

This non-volatile memory can be fabricated by a method for fabricating,for example, the non-volatile memory of claim 1, which comprises thestep of forming an inorganic dielectric layer by depositing an inorganicdielectric on one surface of the organic dielectric thin film in whichfine pores have been formed, the step of covering one end of the poreswith a recording layer by depositing a recording layer and a secondelectrode, in this order, on the surface of the inorganic dielectriclayer, and the step of forming a first electrode onto each pore.

The above-described non-volatile memory can be suitably used in aninformation-recording device or a display device having the followingstructures.

-   -   (1) An information-recording device that comprises a        non-volatile memory, a first clamping member and a second        clamping member that clamp the non-volatile memory therebetween,        and a first elastic member that lies between the non-volatile        memory and the first clamping member;    -   the non-volatile memory comprising an insulating substrate        having a first electrode extending through the substrate from        the front surface to the rear surface thereof, a second        electrode formed on one side of the insulating substrate, and a        recording layer that is clamped between the first electrode and        the second electrode and whose resistance value varies when an        electric pulse is applied across the first electrode and the        second electrode;    -   the insulating substrate having a layered structure composed of        an organic dielectric thin film and an inorganic dielectric        layer that is thinner than the organic dielectric thin film,        with the recording layer being formed on the side on which the        inorganic dielectric layer is formed, and the first electrode        being exposed on the side on which the organic dielectric layer        is formed;    -   the first electrode and the second electrode having a plurality        of memory cells that are formed in the regions where the first        electrode and the second electrode overlay each other as seen in        a plan view, and the second clamping member being provided with        a plurality of first conductive materials on the clamping        surface that are electrically connected to the first electrodes        that correspond to the memory cells; and    -   the memory cells further being provided with a switching        elements that control the application of current to the memory        cells.    -   (2) An information-recording device according to (1), wherein        the first clamping member comprises a clamping surface with a        second conductive material that is electrically connected to the        second electrode and has a second elastic member therebetween.    -   (3) An information-recording device that comprises a        non-volatile memory, a first clamping member and a second        clamping member that clamp the non-volatile memory therebetween;    -   the non-volatile memory having two submemories each containing        an insulating substrate having a first electrode that extends        through the substrate from the front surface to the rear surface        thereof, a second electrode that is formed on one side of the        insulating substrate, and a recording layer that is clamped        between the first electrode and the second electrode and whose        resistance value is changeable by applying an electric pulse        across the first electrode and the second electrode, wherein the        second electrodes of the two submemories face each other with a        first elastic member in between;    -   the insulating substrate having a layered structure composed of        an organic dielectric thin film and an inorganic dielectric        layer that is thinner than the organic dielectric thin film,        with the first electrode being exposed on the side where the        organic dielectric layer is formed;    -   the first electrode and the second electrode having a plurality        of memory cells that are formed in the regions where the first        electrode and the second electrode overlay as seen in a plan        view, and the first clamping member and the second clamping        member being provided with a plurality of first conductive        materials on the clamping surface that are electrically        connected to the first electrodes that correspond to memory        cells and that face the clamping surface; and    -   the memory cells further being provided with switching elements        that control the application of current to the memory cells.    -   (4) An information-recording device according to (3), wherein        the first clamping member and the second clamping member        comprise, on the clamping surface, a second conductive material        that is electrically connected to the second electrode that        faces the clamping surface, with a second elastic member        therebetween.    -   (5) An information-recording device that comprises a        non-volatile memory and an electrically conductive probe that is        movable relative to the non-volatile memory;    -   the non-volatile memory having an insulating substrate that        contains a first electrode that extends through the substrate        from the front surface to the rear surface thereof, a second        electrode that is formed on one side of the insulating        substrate, and a recording layer that is clamped between the        first electrode and the second electrode and whose resistance        value is changeable by applying an electric pulse across the        first electrode and the second electrode;    -   the insulating substrate having a layered structure composed of        an organic dielectric thin film and an inorganic dielectric        layer that is thinner than the organic dielectric thin film,        with the first electrode being exposed on the side where the        organic dielectric layer is formed; and    -   the first electrode and the second electrode having a plurality        of memory cells that are formed in the regions where the first        electrode and the second electrode overlay each other as seen in        a plan view, wherein the electrically conductive probe is        capable of supplying current to the recording layer by being        brought into contact with the first electrode of a predetermined        memory cell.    -   (6) A display device comprising a paper display that is provided        with a non-volatile memory;    -   the non-volatile memory having an insulating substrate that        contains a first electrode that extends through the substrate        from the front surface to the rear surface thereof, a second        electrode that is formed on one side of the insulating        substrate, and a recording layer that is clamped between the        first electrode and the second electrode and whose resistance        value is changeable by applying an electric pulse across the        first electrode and the second electrode; and    -   the insulating substrate having a layered structure composed of        an organic dielectric thin film and an inorganic dielectric        layer that is thinner than the organic dielectric thin film,        with the recording layer being formed on the side where the        inorganic dielectric layer is formed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the main parts of non-volatilememory according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the main parts of non-volatilememory according to another embodiment of the present invention.

FIG. 3 is a cross-sectional view showing the main parts of non-volatilememory according to still another embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating a fabrication process fora non-volatile memory according to one embodiment of the presentinvention.

FIG. 5 is a cross-sectional view illustrating a fabrication process fora non-volatile memory according to another embodiment of the presentinvention.

FIG. 6 is a cross-sectional view schematically illustrating aninformation-recording device according to one embodiment of the presentinvention.

FIG. 7 is a cross-sectional view schematically illustrating aninformation-recording device according to another embodiment of thepresent invention.

FIG. 8 is a cross-sectional view schematically illustrating aninformation-recording device according to still another embodiment ofthe present invention.

FIG. 9 is a perspective view schematically illustrating a display deviceaccording to one embodiment of the present invention.

FIG. 10 is a cross-sectional view showing the structure of anon-volatile memory in the prior art.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described below withreference to the accompanying drawings.

(Non-Volatile Memories)

FIG. 1 is a cross-sectional view showing the main parts of anon-volatile memory according to one embodiment of the presentinvention. As shown in FIG. 1, a non-volatile memory 1 comprises aninsulating substrate 11 that is formed by laminating an inorganicdielectric layer 111 and an organic dielectric thin film 112, recordinglayers 12 and upper electrodes 13 that are formed on the inorganicdielectric layer 111 side of the insulating substrate 11, and a lowerelectrode 14 that is formed on the organic dielectric thin film 112 sideof the insulating substrate 11.

The inorganic dielectric layer 111 is formed of an insulator that isinert to the recording layer 12 during heat generation, and can be anoxide film of SiOx and the like, a nitride film of SiNx and the like, aswell as SiO₂—ZnS, SiO₂—ZnSe, etc. For example, when the inorganicdielectric layer 111 is made of a mixed layer containing SiO₂ and ZnS inthe ratio of SiO₂:ZnS=approximately 0.2:approximately 0.8, it ispossible to make the layer that is deposited on the inorganic dielectriclayer 111 difficult to peel off.

Examples of materials for the organic dielectric thin film 112 includepolyimide, polycarbonate, and like insulative polymers. The organicdielectric thin film 112 is thicker than the inorganic dielectric layer111, and therefore it is possible to reduce the power required to writeor delete data, and to make the substrate 11 readily deformable byelastic bending.

The recording layer 12, which exhibits 2 or more stable conditions, ismade of a phase-change material that is reversibly switchable betweenthe phases and that allows control of variations in its resistance valueattributable to the application of current. Specific examples of usablematerials include chalcogenide based materials, such as Ge₂Sb₂Te₅,Ge₁Sb₂Te₄ and like Ge—Sb—Te compounds, Ag₅In₅Sb₇₀Te₂₀ and likeAg—In—Sb—Te compounds, Te₈₀Sb₅As₁₅ and like Te—Sb—As compounds,Te₈₁Ge₁₅Sb₂S₂ and like Te—Ge—Sb—S compounds, Te₉₃Ge₅As₂ and likeTe—Ge—As compounds, Te₈₀Ge₅Sn₁₅ and like Te—Ge—Sn compounds,Te₆₀Ge₄SnllAu₂₅ and like Te—Ge—Sn—Au compounds, GeTe compounds, etc. Therecording layer 12, which is clamped between an intermediate electrode(first electrode) 18 that will be described later and an upper electrode13 (second electrode), is electrically conductive.

The upper electrode 13 and the lower electrode 14 are made of metalmaterials, such as gold (Au) or the like. A plurality of upperelectrodes 13 and lower electrodes 14 are formed into a striped patternwith equal intervals therebetween, in which the longitudinal directionsof the upper electrodes 13 and the lower electrodes 14 intersect atright angles as seen in a plan view. The regions in which the upperelectrodes 13 and the lower electrodes 14 overlay each other as seen ina plan view compose each memory cell MC. Each memory cell MC can bestructured so as to be electrically separated by using a selectivetransistor, diode, or the like in order to prevent mutual interferencetherebetween. The width of the belt-like portions of the upperelectrodes 13 and the lower electrodes 14 that form a striped pattern isselected depending on the design, and is, for example, not less than 15μm but not more than 100 μm. Of course, it is possible to form belt-likeportions having a width smaller than the above range by employinglithography or FIB (focused ion beam) using light, an electron beam,etc. It is preferable that the intervals between the belt-like portionsbe not less than twice and not greater than ten times the width of thebelt-like portions.

On the positions corresponding to each memory cell MC, the insulatingsubstrate 11 comprises a large number of fine pores 16 that extendthrough the substrate from the front surface to the rear surfacethereof. A portion of the inorganic dielectric layer 111 enters in andadheres to the inner wall surface of the pore 16, forming a ring-shapedheat-resistant protective film 17 that is continuously connected to theinorganic dielectric layer 111. In the pore 16, which is covered by alower electrode 14 on its lower end, an intermediate electrode 18 thatis made of, for example, rhodium (Rh) is filled. The recording layer 12and the lower electrode 14 are electrically connected by thisintermediate electrode 18. In the memory cell MC, the upper portion ofthe intermediate electrode 18 is covered by the upper electrode 13, andthe intermediate electrode 18 is electrically connected to the upperelectrode 13 via the recording layer 12.

In the thus constructed non-volatile memory 1, data can be written to,read or deleted from a predetermined memory cell MC by selecting theupper electrode 13 and the lower electrode 14 corresponding to thememory cell MC and applying a suitable electric pulse across theselected electrodes. More specifically, to write data, an electric pulseis applied to the electrodes with a predetermined voltage to produceJoule heat, thereby changing the recording layer 12 from an amorphousstate to a crystalline state and lowering the resistance value thereof.To delete data, on the other hand, an electric pulse having a pulsewidth shorter than that for writing is applied to rapidly cool the hightemperature of the recording layer 12, thereby changing the layer 12from a crystalline state to an amorphous state and raising theresistance value thereof. To read data, a voltage lower than that forwriting or deleting is applied to detect the current value that is basedon the resistance value variation.

In the present embodiment, the recording layer 12 is formed on thesubstrate 11 on the side where the inorganic dielectric layer 111 isformed. Therefore, it is possible to restrain the heat that is generatedaround the joint portion between the recording layer 12 and theintermediate electrode 18 due to the application of current forrecording or deleting data from being transmitted to the organicdielectric thin film 112. Therefore, it is possible to preventdecomposition of the organic dielectric thin film 112 due to the rise oftemperature. This prevents deterioration of the recording layer 12 andintermediate electrode 18, and increases the number of possible datarecording or deleting cycles to or from the memory cell MC. Furthermore,because the heat-resistant protective film 17 that is made of aninorganic dielectric is formed on the inner wall surface of the pore 16,it is possible to restrain the heat that is generated around the jointportion between the recording layer 12 and the intermediate electrode 18from being transmitted to the organic dielectric thin film 112.

If the inorganic dielectric layer 111 is too thin, the thermalprotection effect for the organic dielectric thin film 112 becomesinsufficient. On the other hand, if the organic dielectric thin film 112is too thick, effects such as the reduction in power consumption thatare achieved by the use of the organic dielectric thin film 112 becomeinsufficient. Therefore, it is preferable that the thickness of theinorganic dielectric layer 111 be not less than 2 nm but not more than50 nm. It is preferable that the thickness of the organic dielectricthin film 112 be not less than 100 nm but not more than 10,000 nm.

The structure of the non-volatile memory 1 is not limited to theabove-described structure, and several modifications can be added. Forexample, as shown in FIG. 2 or FIG. 3, it is possible to dispose one ormore intermediate electrodes 18 on each region of the memory cell MC byusing a substrate 11 having a large number of fine pores 1 b randomlyarranged therein. This eases the limitations on the positions in whichthe recording layer 12 can be formed, increasing the design flexibility.It is also possible to enhance the insulation property between thememory cells MC by forming a separate upper electrode 13 and recordinglayer 12 for each memory cell MC. Instead of disposing the upperelectrodes 13 and lower electrodes 14 into a striped pattern, it is alsopossible, for example, to form the upper electrode 13 on one entiresurface of the substrate and dispose the lower electrodes 14 in amatrix.

In the present embodiment, the recording layer 12 can be accessed bydisposing the upper electrode 13 and the lower electrode 14 on the frontand rear surfaces of the insulating substrate 11; however, as describedlater, if the recording layer is structured so as to be clamped betweenthe intermediate electrode (first electrode) and the upper electrode(second electrode), the lower electrode is not absolutely necessary.

(Method for Fabricating a Non-Volatile Memory)

Hereunder, a method for fabricating a non-volatile memory will beexplained by taking the non-volatile memory shown in FIG. 2 as anexample.

First, as shown in FIG. 4(a), a 6-μm-thick organic dielectric thin film112 made of polycarbonate was prepared, in which a large number of finepores 16 having a diameter of 100 nm were formed substantiallyperpendicular to the surface thereof. Methods for forming a large numberof fine pores in a film are disclosed in, for example, thespecifications of U.S. Pat. No. 6,060,743 (Japanese Unexamined PatentPublication No. 1999-40809) and Japanese Unexamined Patent PublicationNo. 1999-170378. In the present embodiment, after irradiating thesurface of the organic dielectric thin film with an ion beam heldperpendicular to the surface to form an ion track, the ion track wasselectively etched by dipping the film into an etching solution torandomly form a large number of fine pores. Such a forming method doesnot employ lithography techniques, and therefore it is possible toobtain fine pores at low cost even when the diameter of the pore is assmall as approximately 100 nm. It is preferable that, by adjusting theetching time or the like, the diameter of the fine pores 16 becontrolled to a predetermined value to obtain a preferable aspect ratio,which will be described later.

Then, as shown in FIG. 4(b), the organic dielectric thin film 112 wasplaced on a susceptor S of a sputtering device, and SiO₂, which is aninorganic dielectric, was deposited thereon to form an inorganicdielectric layer 111 on the organic dielectric thin film 112, thusobtaining an insulating substrate 11. The amount of inorganic dielectricdeposited was such that the fine pores 16 were not completely closed. Inthe present embodiment, the deposition of SiO₂ was stopped when thediameter of the openings of the fine pores 16 narrowed from 100 nm to 50nm. At this time, the thickness of the inorganic dielectric layer 111was approximately 30 nm.

The condition of the inorganic dielectric that is deposited on theorganic dielectric thin film 112 varies depending on the aspect ratio ofthe pores 16 (the aspect ratio is obtained by dividing the height of thepore 16 by the diameter of the pore 16). When the aspect ratio is notless than 10 but not more than 100 as in the present embodiment, aninorganic dielectric will be deposited on the organic dielectric thinfilm 112 and, at the same time, will adhere to the inner wall surface ofthe pore 16 around the opening thereof, forming a ring-likeheat-resistant protective film 17, as shown in FIG. 4(b). When theaspect ratio of the pore 16 is not less than 10 but not more than 100,the thickness of the heat-resistant protective film 17 inside the pore16 becomes thinner toward the lower portion (in FIG. 1, in the directionfrom the upper electrode (second electrode) 113 toward the intermediateelectrode (first electrode) 118 and the lower electrode 14). In otherwords, there are some portions in which the inside diameter of the pore16 becomes larger in the direction from the upper portion to the lowerportion due to the heat-resistant protective film 17 that is formedaround the inner wall surface thereof.

This heat-resistant protective film 17 can effectively restrain the heatthat is generated around the interface between the recording layer 12and the intermediate electrode 18 due to application of current frombeing transmitted to the organic dielectric thin film 112. Furthermore,the formation of a narrow current-carrying part of the intermediateelectrode 18 due to the heat-resistant protective film 17 increases thecurrent density, making it possible to reduce the power consumption ofthe product.

On the other hand, if the aspect ratio of the fine pore 16 is one ormore and less than 10, the inorganic dielectric can easily enter thefine pores 16, and therefore the ring-like heat-resistant protectivefilm 17 as shown in FIG. 4(b) can be formed not only around the openingsof the fine pores 16 but also on the entire inner wall surfaces of thefine pores 16 in such a manner that the thickness of the film becomessubstantially uniform. In other words, when the aspect ratio of the finepore 16 is one or more and less than 10, regardless of the presence ofthe heat-resistant protective film 17 therein, the inside diameter ofthe fine pore 16 becomes substantially uniform from the top to thebottom thereof.

In this case, the above-described narrow current-carrying part is notformed in the intermediate electrode 18; however, the thermal protectiveeffect of the heat-resistant protective film on the organic dielectricthin film 112 can be enhanced.

In such a process for depositing an inorganic dielectric, a small amountof the inorganic dielectric enters the fine pores 16 and is deposited onthe susceptor S. When the organic dielectric thin film 112 is removedfrom the susceptor S, some of the inorganic dielectric remains in thefine pores 16 as residue R. Therefore, after forming the inorganicdielectric layer 111, it is necessary to eliminate the residue R byremoving the organic dielectric thin film 112 from the susceptor S andsupplying gas into the fine pores 16 from the inorganic dielectric layer111 side. In this case, it is necessary to remount the organicdielectric thin film 112 on the susceptor S, which makes the processcomplicated.

Therefore, in the process for forming the inorganic dielectric layer111, instead of directly attaching the organic dielectric thin film 112onto the surface of the susceptor S, it is possible to form a gapbetween the organic dielectric thin film 112 and the susceptor S byproviding a spacer SP therebetween as shown in FIG. 5. The inorganicdielectric that has entered the fine pores 16 thus does not remaininside the fine pores 16 and reaches the surface of the susceptor S.This eliminates the need to remove the organic dielectric thin film 112from the susceptor S after depositing the inorganic dielectric, andthereby enables the subsequent process to be promptly started.

Next, as shown in FIG. 4(c), a recording layer 12 was formed bysputtering a memory material made of Ge₂Sb₂Te₅ on the inorganicdielectric layer 111 side of the substrate using a metal mask, and thenan upper electrode 13 was formed on one entire surface of the substrateby further sputtering Au on the recording layer. As a memory material,for example, the use of GeSb₂Te₄ having various chemical constituentratios is effective for extending the service life of the productbecause the melting point of the memory material becomes relatively low.The openings of the fine pores 16 in which the diameters have beennarrowed by the formation of the inorganic dielectric layer 111 thusbecome covered with the recording layer 12 that has been formed bydepositing the memory material.

Intermediate electrodes were then formed in the fine pores 16. Formationof the intermediate electrodes can be performed by employing asputtering method, remote sputtering method, electroplating method, orother method; however, in the present embodiment, the electroplatingmethod was employed. As shown in FIG. 4(d), a plating solution L wasprepared by dissolving the positive ions of the plating metal in anacidic solution, wherein a metal plate M composed of Au or the like,which is insoluble in the plating solution L, formed a positiveelectrode, and the recording layer 12, whose surface was exposed to theinside of the pores 16 formed a negative electrode. A power source wasconnected to the electrodes and the negative electrode was therebyelectroplated. It is preferable that the upper electrode 13 and theconductive plate that is composed of the metal plate M, etc., beparallel as shown in FIG. 4(d). This will allow the insides of the finepores 16 to be gradually filled with the plating metal, and the platingto be stopped when the insides of the fine pores 16 are completelyfilled, thereby producing the intermediate electrodes 18. Rh, Ru, Pt,Au, Cu, and the like are preferable as plating metals. Materials such asCu and the like that are usable for the multilayer interconnection ofULSIs, in particular, are easily obtainable at low cost.

The timing for stopping the electroplating can be determined bymeasuring the relationship between the quantity of the plated metal andthe plating time in advance, and estimating the time necessary for theplating metal to fill the fine pores 16. Alternatively, it is alsopossible to determine the timing for stopping the plating by utilizingthe fact that the plated surface changes color depending on the amountof the plated metal. In other words, immediately before the fine pores16 are filled with the plating metal, the visible part of the platedsurface appears black; however, when the insides of the fine pores 16are completely filled with the plating metal and the plated surfaceextends along the surface of the insulating substrate 11, the platedsurface turns from black to white. Therefore, plating can be stoppedwhen the plated surface turns white. Furthermore, in addition to thecolor change of the plated surface, it is also possible to determine thetiming for stopping the plating from the fact that when plating is doneat a constant voltage, a kink appears in the time-related change in thecurrent value (or in the time-related change in the voltage value whenplating is done at a constant current).

Lastly, the formation of a non-volatile memory as shown in FIG. 2 iscompleted by forming lower electrodes 14 in the form of a matrix bysputtering Au on the rear surface of the insulating substrate 11 (on theorganic dielectric thin film 112 side) using a metal mask. The number ofdata rewiring cycles was measured for this non-volatile memory, and itwas a minimum of 10⁴, resulting in a satisfactory writing life time.

In a structure as shown in FIG. 3, the intermediate electrode 18 isformed by plating the lower electrode 14, which has been formed inadvance, and then forming the recording layer 12 and the upper electrode13. The electroplating can be done to the lower electrode 14, which isformed of metal, and this is advantageous in that it enables a highlevel of plating control.

(Information-Recording Devices)

FIG. 6 is a cross-sectional view schematically illustrating aninformation-recording device according to one embodiment of the presentinvention. The information-recording device shown in FIG. 6 comprises anon-volatile memory 31, a pair of clamping members that clamps thenon-volatile memory 31 therebetween (a first clamping member 321 and asecond clamping member 322), and elastic members (a first elastic member331 and a second elastic member 332) that are made of rubber or the likeand held between the non-volatile memory 31 and the first clampingmember 321. The first elastic member 331 is fixed on the surface of theupper electrode 13 in such a manner that a portion of the upperelectrode 13 of the non-volatile memory 31 is exposed. It is alsopossible to attach a label describing the characteristics (the name ofthe company that manufactured the memory, the content of the recordeddata, etc.) of the non-volatile memory 31 on the surface of the firstelastic member 331.

The non-volatile memory 31 has a structure in which a lower electrode 14is omitted from the non-volatile memory 1 shown in FIG. 2, but in otherrespects, the structure thereof is the same as the non-volatile memory 1shown in FIG. 2. Therefore, the same reference numbers are used for thesame constituent components thereof and a detailed explanation isomitted.

The first clamping member 321 and the second clamping member 322 arecomposed of a hard plastic, etc., having high rigidity, and eachcomprises a second conductive material 323 and a first conductivematerial 324 on its clamping surface, respectively. Between the pair ofthe clamping members 321 and 322, spring members 325 and 326 that serveas a biasing means for holding the non-volatile memory 31 therebetween.

The second conductive material 323 is mounted on a clamping surface ofthe first clamping member 321 with the second elastic member 332therebetween. The second conductive material 323 is designed so as to beelectrically connectable to the entire exposed portion of the upperelectrode 13. Furthermore, the first conductive materials 324 are formedin a matrix and mounted on the clamping surface of the second clampingmember 322, and are electrically connected to the intermediateelectrodes 18. To the first conductive material 324, a switching element328 is connected so that it can control the ON/OFF of the application ofcurrent to the recording layer 12 via the first conductive material 324.In the present embodiment, the switching element 328 is formed from aselective transistor that is made of Si, etc.; however, it is alsopossible to use a pn junction diode, a Schottky diode and the like.

With information-recording device structured in this way, from thecondition shown in FIG. 6, the second conductive material 323 comes incontact with the upper electrode 13 and the first conductive material324 comes in contact with the intermediate electrode 18 by the action ofthe spring members 325 and 326, and the non-volatile memory 31 isthereby clamped between the pair of clamping members 321 and 322.

Because the first elastic member 331 and the second elastic member 332lie between the first clamping member 321 and the non-volatile memory31, the non-volatile memory 31 and the second clamping member 322 canuniformly contact each other due to the pressure generated by theelastic members, and the electric contact between the first conductivematerial 324 and the intermediate electrode 18 is thereby reliablyensured. In addition, in the present embodiment, because an organicdielectric thin film 112 that is easily deformed by elastic bending isdisposed so as to contact the clamping surface of the second clampingmember 322, the contact between the non-volatile memory 31 and thesecond clamping member 322 can be further improved. It is also possibleto dispose the first elastic member 331 on the first clamping member 321instead of on the non-volatile memory 31. In this case, the firstelastic member 331 and the second elastic member 332 can be configuredinto a single-unit structure.

Access to a memory cell can be performed by turning the switchingelement 328 that corresponds to the selected memory cell to an ON state.Data can be written by supplying electric power to the recording layer12 of the accessed memory cell to generate heat, thereby changing therecording layer from an amorphous state to a crystalline state, andlowering the resistance thereof. Data can be read by measuring theresistance value of the recording layer 12 of the accessed memory cell.Data can be deleted by rapidly cooling the recording layer 12 of theaccessed memory cell that has been heated by applying electric power,thereby changing the recording layer from a crystalline state to anamorphous state to increase the resistance thereof.

The specific structure of the information-recording device is notlimited to the above-described embodiment, and various modifications canbe added. For example, the information-recording device as shown in FIG.7 comprises a non-volatile memory 41, a pair of clamping members (afirst clamping member 421 and a second clamping member 422) that clampthe non-volatile memory 41 therebetween, and elastic members (a firstelastic member 431 and a second elastic member 432) made of rubber,flexible plastic, etc., which are held between the non-volatile memory41 and the first clamping member 421.

The non-volatile memory 41 is formed by using the non-volatile memory 31of FIG. 6 as a submemory, and uniting two submemories in such a mannerthat the upper electrodes 13 of the submemories face each other with afirst elastic member 431 therebetween, wherein a portion of the upperelectrode 13 of each submemory is exposed.

The first clamping member 421 and the second clamping member 422 aremade of a hard plastic, etc., having high rigidity. Both the secondconductive material 423 and the first conductive material 424 aredisposed on each clamping surface. Spring members 425 and 426, whichserve as biasing means for clamping the non-volatile memory 41, aredisposed between the pair of clamping members 421 and 422.

The second conductive materials 423 are disposed on the clampingsurfaces of the clamping members 421 and 422 with the second elasticmembers 432 disposed therebetween so as to be electrically connectableto the exposed portions of the upper electrodes 13. Furthermore, aplurality of first conductive materials 424 are mounted on the clampingsurfaces of the clamping members 421 and 422 by being formed into amatrix and are electrically connectable to the intermediate electrodes18. A switching element 428 is connected to the first conductivematerial 424 so that application of current to the recording layer 12can be turned ON/OFF via the first conductive material 424. In thepresent embodiment, the switching element 428 is formed from a selectivetransistor made of Si or the like; however, it is also possible to usepn junction diodes, Schottky diodes, etc.

An information-recording device structured in this way can also achievethe same effects as the information-recording device of FIG. 6.Furthermore, since an information-recording device structured in thisway can obtain twice the memory capacity of the information-recordingdevice of FIG. 6, it can meet demands for increased memory capacity.

In the above-described information-recording device, access to apredetermined memory cell can be achieved by methods other than thatdescribed above, wherein a switching element is used. For example, in anon-volatile memory as shown in FIG. 2, a memory cell can be accessed byusing an electrically conductive probe.

In FIG. 8, an electrically conductive probe 51 is structured so as to bemovable in the vertical and horizontal directions by a transferringmechanism 52. In order to access a memory cell, first, the electricallyconductive probe 51 is brought near to the exposed surface e of theintermediate electrodes 18 to such a degree that the probe does not comeinto contact with the exposed surface e and is transferred to thepredetermined memory cell in parallel to the exposed surface e. Then,the electrically conductive probe 51 is brought into contact with theexposed surface e, and, after writing, reading, or deleting data, theelectrically conductive probe 51 is separated from the exposed surfacee. In the present embodiment, the electrically conductive probe 51 comesinto contact with the surface of the organic dielectric thin film 112which deforms easily by elastic bending, and therefore increasing thecontact of the electrically conductive probe 51 and ensuring reliableelectrical contact thereof.

Instead of configuring the electrically conductive probe 51 so as to bemovable, it is also possible to employ a structure in which thenon-volatile memory 31 is movable (including rotary movement) while theelectrically conductive probe 51 is fixed, or one in which both theelectrically conductive probe 51 and the non-volatile memory 31 aremovable. Alternatively, it is possible to form a plurality ofelectrically conductive probes 51 in such a manner that eachelectrically conductive probe 51 is independently controllable.

(Display Devices)

The power consumption of the non-volatile memories according to theforegoing embodiments can be reduced when writing or deleting data,therefore making them useful for various applications. These memoriesare usable, for example, for a paper display as shown in FIG. 9.

FIG. 9 shows a paper display 61 comprising a non-volatile memory 62disposed on the rear surface thereof, a display 63 disposed on the frontsurface thereof for displaying characters and images, wherein aplurality of paper displays are bound together. The paper display 61 canbe fabricated using known techniques, such as that disclosed by JapaneseUnexamined Patent Publication No. 1999-502950. The non-volatile memory62 shown in FIG. 1 can be employed. The characters and images to beshown on the paper display 61 can be stored in the non-volatile memory62 as data, then transferred automatically or manually to the display63, in order to change the displayed characters or images.

In this structure, the data to be displayed is stored in a non-volatilememory that is able to conform to the changing shape of the foldable andcurvable paper display. Therefore, it allows characters or images to bechanged without impairing the ability of the paper display to changeshape, and the pages can be turned without any unnatural feeling.

The non-volatile memory 62 can be configured so as to easily removablefrom the paper display 61, thereby allowing the removed non-volatilememory 62 to be mounted to a data playback device (not shown) and thedigital data for the recorded content and display content to be importedinto a computer and used.

INDUSTRIAL APPLICABILITY

As described above, the present invention can provide a non-volatilememory that can increase the maximum possible number of data writingcycles while lowering power consumption.

1-11. (canceled)
 12. A method for fabricating a non-volatile memory thatcomprises an insulating substrate having a first electrode extendingthrough the substrate from the front surface to the rear surfacethereof; a second electrode that is formed on one side of the insulatingsubstrate; and a recording layer that is clamped between the firstelectrode and the second electrode and whose resistance value varieswhen an electric pulse is applied across the first electrode and thesecond electrode; wherein the insulating substrate has a layeredstructure composed of an organic dielectric thin film and an inorganicdielectric layer that is thinner than the organic dielectric thin film;with the recording layer being formed on the side on which the inorganicdielectric layer is formed, and comprising the steps of: forming theinorganic dielectric layer by depositing inorganic dielectric on onesurface of the organic dielectric thin film in which a fine pore hasbeen formed; covering one end of the pore with the recording layer bydepositing the recording layer and the second electrode on the surfaceof the inorganic dielectric layer in this order; and forming the firstelectrode in the pore.
 13. A method for fabricating a non-volatilememory according to claim 12, wherein the step of forming the inorganicdielectric layer comprises the step of: forming a heat-resistantprotective film that is made of an inorganic dielectric on at least oneportion of the inner wall surface of the pore.
 14. A method forfabricating a non-volatile memory according to claim 13, wherein theaspect ratio of the pore in the organic dielectric thin film is not lessthan 1 but less than
 10. 15. A method for fabricating a non-volatilememory according to claim 13, wherein the aspect ratio of the pore inthe organic dielectric thin film is not less than 10 but not more than100.
 16. A method for fabricating a non-volatile memory according toclaim 12, wherein the step of forming the inorganic dielectric layercomprises the step of: mounting the organic dielectric thin film on thesurface of a susceptor with a spacer therebetween, and depositing aninorganic dielectric thereon.
 17. A method for fabricating anon-volatile memory according to claim 12, wherein the step of formingthe first electrode in the pore comprises the steps of: dipping theorganic dielectric thin film having fine pores formed therein into aplating solution that contains metal ions used for forming the firstelectrode and has an insoluble conductive plate therein; and applyingcurrent across the second electrode and the insoluble conductive plate.